It is beneficial for corporations that deploy medium to large Wireless Local Area Network (WLAN) infrastructures to effectively manage energy costs, including energy costs for associated access points, without adversely affecting coverage and end user performance. A typical access point in a WLAN may consume about 10-16 Watts of power, depending on a number of factors including, the number of radio frequency chains that are active within the access point. It has been noted that a small subset of the total deployed access points in a network may be used during the day. Even fewer of these access points may be used at nights and on weekends, depending upon the primary function of the network. Hence, a majority of the access points in a medium to large WLAN may be idle for long periods of time.
In a WLAN configuration with hundreds of access points, energy consumption by under-utilized access points can be significant. Some of these WLAN installations may implement an always-on power saving scheme, a threshold-based power saving scheme, or a schedule-based power saving scheme. It will be appreciated by those of ordinary skill in the art that costs associated with the always-on scheme are significant. Yet threshold-based schemes or schedule-based power saving schemes may cause either signal-strength degradation or impact coverage/availability during the switch off periods. For example, access points have a finite initialization time from a cold start to a beaconing ready state when capable of associating with an associated client device. Therefore, a power saving scheme that completely powers down an access point may not be capable of re-initializing the access point in time to allow it to function as a reserve resource. Furthermore, a fully powered-down access point also may need to be minimally self powered by, for example battery or solar components, so that is can be remotely switched on again.
WLAN client devices can include any wireless communication device such as mobile radios, cellular telephones, personal computers, personal digital assistants (PDAs), and the like. In most situations, client devices are associated with an access point from a geographical location of frequent usage, where the client device is most likely to remain stationary and associated with a single access point for a period of time. An example of a location of frequent usage may be an assigned desk in a corporate office, an internet café, an airport gate waiting area, or a checkout aisle of a department store. Such stationary usage of WLANs makes it easy to predict when to power off particular access points in the WLAN. However, as more mobile devices operate within WLANs, the WLANs need to be configured to effectively handle these mobile units during low network utilization periods, with the reliability of an always-on power saving scheme.
Accordingly, there is a need for efficiently conserving the power usage of access points in a WLAN during low network usage intervals, without impacting coverage to users of the WLAN.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.